It has long been known to manufacture and distribute pressure-sensitive adhesive labelstock for labels by providing a layer of a face or facestock material for the label or sign backed by a layer of pressure sensitive adhesive and PSA which in turn, generally is covered by a release liner or carrier. The liner or carrier protects the adhesive during shipment and storage and allows for efficient handling of an array of individual labels after the labels are die-cut and the matrix is stripped from the layer of facestock material and up to the point where the individual labels are dispensed in sequence on a labeling line. During the time from die-cutting to dispensing, the liner or carrier remains uncut and may be rolled and unrolled for storage, transit and deployment of the array of individual labels carried thereon.
Failure to reliably dispense is typically characterized by the label following the carrier around a peel plate without dispensing or “standing-off” from the carrier for application to the substrate. Such failure to dispense is believed to be associated with excessive release values between the label facestock material and the liner. Dispensability also is dependent upon the stiffness of the facestock. Failure to dispense may also be characterized by the wrinkling of the label due to lack of label stiffness at the dispensing speed as it is transferred from the carrier to the substrate. Another particular need in labeling applications is the ability to apply polymeric-film labels at high line speeds, since an increase in line speed has obvious cost saving advantages.
There is also a growing need for down-gauging of label films in order to improve the cost performance ratio of labelstock. A disadvantage of down-gauging of films is that the stiffness in the machine direction will become too low to guarantee good dispensing of the labels. This problem has been overcome in the past by utilizing materials having a higher modulus of elasticity and, hence, higher stiffness.
Polypropylenes, and in particular biaxially oriented polypropylene (BOPP), have been utilized successfully in down-gauging applications since polypropylene is relatively inexpensive and exhibits sufficient stiffness to dispense well. However, polypropylenes in general exhibit relatively high tensile modulus values in both machine-direction and cross-direction which results in labels that are not very conformable, and polypropylenes are not easily printable with UV based inks that are most commonly used to print on pressure sensitive labels. Accordingly, it is common practice to improve the printability of polypropylene by adding a print skin (by coextrusion) or a print receptive coating. These solutions, however, add complexity and costs to the production process.